For the most part, modern motor vehicles have an electronic stability system, e.g., ABS (anti-lock braking system) and/or ESP (electronic stability program) which provides for stabilization of the vehicle from the standpoint of driving dynamics, e.g., during braking, and thus assists the driver in guiding the vehicle. The driver is generally unable to either influence or override the actions of these stability systems.
On the other hand, there are assistance systems which assist the driver on another level in guiding the vehicle. Examples of such assistance systems are so-called ACC (adaptive cruise control) systems which permit automatic speed control and automatic distance control with respect to the preceding vehicle, warning systems which warn the driver of critical traffic situations, and pre-crash systems which, in the event of an imminent collision, automatically trigger actions for averting the collision or for lessening the collision results. To detect the traffic situation, these assistance systems generally have a surround field sensor system, e.g., in the form of radar sensors, video systems having electronic image processing and the like, and depending on the traffic situation sensed, variably intervene in the drive system and, if necessary, in the brake system of the vehicle, as well. In general, the driver is able to deactivate these systems and override their commands.
For the intervention in the brake system, the assistance systems have a triggering unit which, depending on the situation, outputs a braking demand that the vehicle braking unit then converts into the corresponding braking action. The intensity of the braking action can vary within a wide range, and extends from gentle braking actions for adjusting to the speed of the preceding vehicle, to brief warning brakings which serve as kinesthetic warning signal for the driver, right up to automatically triggered emergency brakings. During these braking actions, generally the driver at least retains control over the steering of the vehicle, so that the driver is able to undertake evasive maneuvers. In this context, if necessary, the stability system automatically provides for the dynamic stabilization of the vehicle, so that the vehicle does not get out of control.